USPTO Patents Application 09828203

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WORLD INTELLECTUAL PROPERTY ORGANIZATION
International Bureau

INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)

(51) International Patent Classiflcation ^
G05D 22/02

Al

(11) International Publication Number: WO 92/21080 ^

(43) International Publication Date : 26 November 1992 (26. 1 1 .92)

(21) International Application Number: PCT/GB92/00910

(22) International Filing Date : 20 May 1992 (20.05.92)

(30) Priority data:
9111065.0

22 May 1991 (22.05.91)

GB

(71) Applicant (for all designated States except US): PROTIME-

TER PLC [GB/GB]; Meter House, Fieldhouse Lane,
Marlow, Buckinghamshire SL7 ILX (GB).

(72) Inventor; and

(75) Inventor/Applicant (for US only) : DADACHANJI, Fali,
Minccher [GB/GB]; 32 Highfield Park, Mariow, Buck-
inghamshire SL7 2DE (GB).

(74) Agent: LESLEY, Sheila, F.; Forrester Ketley & Co., For-
rester House, 52 Bounds Green Road, London Nil 2EY
(GB).

(81) Designated States: AT (European patent), AU, BB, BE
(European patent), BF (OAPI patent), BG, BJ (OAPI
patent), BR, CA, CF (OAPI patent), CG (OAPI patent),
CH (European patent), CI (OAPI patent), CM (OAPI
patent), DE (European patent), DK (European patent),
ES (European patent), FI, FR (European patent), GA
(OAPI patent), GB (European patent), GN (OAPI pa-
tent), GR (European patent), HU, IT (European patent),
JP, KP, KR, LK, LU (European patent), MC (European
patent), MG. ML (OAPI patent), MR (OAPI patent),
MW, NL (European patent), NO, PL, RO, RU. SO, SE
(European patent), SN (OAPI patent), TD (OAPI pa-
tent), TG (OAPI patent), US.

Published

With international search report.

(54) Title: APPARATUS FOR, AND METHOD OF, PROVIDING AN ATMOSPHERE OF PREDETERMINED HUMIDI-
TY

—

22

(57) Abstract

An apparatus for providing an atmosphere of predetermined humidity comprises a chamber (10), a source (22) of dry air,
leading to the chamber (10) directly via a valve (V3) and a saturator (20) having an inlet connected with the source (22) and an
outlet connected with the chamber (10) via a valve (VI). An outlet from chamber (10) is connected via a valve (V2) with an extrac-
tor, whereby with valves V2 and VI open and valve V3 closed, saturated air can be drawn into chamber (10) whilst with valves V2
and V3 open and valve VI closed dry air can be drawn into chamber (10), to adjust the humidity in the chamber (10) in either
case. A relative humidity sensing probe (12) and a temperature sensing probe (14) within chamber (10) pass signals to a computer
(24) which controls valves VI, V2, and V3, whereby feed-back regulation of the humidity in chamber (10) can be achieved.

FOR THE PURPOSES OF INFORMATION ONLY

Codes used lo identify Stales party to the PCT on the front pages of pamphlets publishing international
applications under the PCI*.

AT

Austria

FI

iMnland

Ml

Man

All

Aiisitraliu

FR

France

MN

Mongolia

BB

CA

(Jabon

MR

Mauritania

BE

BuJgiuiii

CB

MW

Malawi

BF

Burkina ha:»u

ON

Guinea

NL

Neihcrland:>

BC

Bulgaria

GR

(jruccu

NO

Norway

BJ

Benin

Hti

Hungary

PL

Poland

BR

Bra/it

IE

Ireland

RO

Romania

CA

C anatJa

IT

ilaly

RU

Ku&bian Federation

CF

C^ciUral African Kcpublic

JP

JafKin

SD

Sudan

CG

Congo

KP

lJemucra[ic People 'b Keptibtie

SE

Sweden

CH

Swil/crlantJ

uf Korea

SN

Senegal

CI

C'dtc J'lvuin:

KR

Republic of Korea

SU

Soviet Union

CM

C'amcroun

LI

t iechtenatein

TD

Chad

CS

C VcchcKiluvaLia

LK

Sri loinka

TG

Togo

Cfurniany

LU

Luxcniliourg

US

United States of America

UK

I>cnmark

MC

Monaco

ES

MG

Matlagabcar

wo 92/21080

PCr/GB92/00910

1

Title: "Apparatus for, and method of, providing an
atmosphere of predetermined humidity"

THIS INVENTION relates to an apparatus for and a method of
providing an atmosphere of predetermined humidity^, for
example for use in calibrating humidity measuring
instruments or for storing items which require to be kept
at a particular humidity.

A number of methods are available for providing
atmospheres of known humidities. One traditional method is
to mix wet air with differing quantities of dry air to
produce different humidities. Another method is to
maintain the volume of air concerned over a solution of
saturated salts and in moisture equilibrium with the
latter. These known methods are expensive and/or time
consuming .

It is among the objects of the present invention to
provide an improved apparatus for and method of, providing
an atmosphere of predetermined humidity.

According to one aspect of the invention there is
provided apparatus for providing an atmosphere of
predetermined humidity, comprising a chamber for containing
such atmosphere, means for supplying dry air and moist air
to said chamber and means for drawing air from said
chamber, control means for controlling the relative amounts
of dry air and moist air supplied to the chamber to afford
a coarse adjustment of humidity, and fine control means
including moisture removal means for removing moisture from
the atmosphere in said chamber, the apparatus including a
control facility controlling said dry and moist air

wo 92/21080

PCr/GB92/00910

2

supplying means ^ and said means for drawing air from the
chamber, and/ or controlling said moisture removal means,
said humidity sensing means providing its output signal to
said control facility.

An embodiment of the invention is described below,
by way of example, with reference to the accompanying
schematic block diagram.

Referring to the block diagram, the apparatus
includes a small chamber 10 within which are placed a
reference dewpoint or relative humidity measuring probe 12
and a temperature sensing probe 14 .

Exposed within the chamber, for example forming one
wall of the chamber, or part of one wall,, is a surface,
indicated at 16, of which the temperatxire can be closely
controlled, and which, more particularly, can be cooled
with respect to its surroundings, for example thermo-
electrically using a Peltier cooling device (indicated
schematically at 18) or by passing a cool liquid through
passages within a metal body affording the surface 16. If
desired, several walls of the chamber 10 may have such
surfaces 16 which can be controllably cooled in the manner
indicated.

The chamber 10 is connected via a valve V2 with an
air extractor or suction pump, via a valve VI with an air
saturator 20 and via a valve V3 with a source 22 of dry
air. When valves VI and V2 are open and the extractor or
pump operated, dry air is drawn from the source 22, via an
air conduit into the saturator 20 and, in passing through
the saturator 20, becomes saturated with moisture. The
saturated air then passes, via the valve VI, into the
chamber 10.

wo 92/21080

PCT/GB92/00910

3

The valves VI, V2 and V3 are electrically operable
valves controlled by a computer 24, for example a
microcomputer/ having a keyboard 2 6 and a display 28. The
humidity probe 12 and the temperature probe 14 provide
electrical signals, significant of the respective values
sensed to the computer 24, In practice, for precision, the
humidity sensor may operate by measurement of dewpoint, for
example in a repeating cycle.

The system functions as follows:

If a known humidity (or dewpoint) is required, this
number is simply entered into the computer 24 by the action
of the keyboard 26. The computer then determines, on the
basis of the signals from the probe 12, whether the
atmosphere already present in chamber 10 needs to be
humidified or de-humidified. If the atmosphere needs to be
humidified, then valves VI and V2 are opened and saturat d
air flows into the chamber until such time as there is a
slight excess of water vapour in the measuring chamber
(i.e. if the required dewpoint was 5^0, saturated water
vapour would be allowed to flow until the dewpoint was say,
10*»C) • VI and V2 are then closed. Conversely, if the
chamber moisture content is too high, then VI is shut and
V2 and V3 are opened to allow dry air to flow through the
chamber until the moisture content is merely slightly in
excess of the desired amount.

Thus, at this stage there is confined within
chamber 10 an amount of air at a dewpoint slightly higher
than the required dewpoint. The surface 16 is now cooled
until condensation foirms on the surface and the surface 16
is kept cool until sufficient condensation is deposited on
th surface 16 (and thus removed from the atmosphere within
chamber 10) to dry the atmosphere in chamber 10 down to the

wo 92/21080

PCT/GB92/00910

4

desired dewpoint^ as sensed by the probe 12. The digital
computer 24 thus forms part of a control loop which keeps
the temperature of surface 16 adjusted to remove precisely
the amount of water from the atmosphere in the chamber 10
to keep the dewpoint at precisely the required dewpoint.
The temperature of the chamber is constantly measured by
the temperature measuring probe 14 and both these signals
of temperature and dewpoint are fed to the computier 24
which can calculate the relative humidity or the moisture
content of the atmosphere as required, and, for example,
display the calculated value on display 28. Indeed,
facilities preferably exist in the software programming of
the instrument to allow the desired control point to be
entered either as dewpoint or relative humidity or moisture
content. The overall temperature of the chamber 10 may be
regulated, for example utilising further heating and/ or
cooling means (not shown) controlled by the computer 24 in
a further control loop, to minimise the extent to which
moisture must be added to or removed from the atmosphere in
the chamber to maintain a predetermined relative humidity.

wo 92/21080

PCT/GB92/00910

CLAIMS

1. Apparatus for providing an atmosphere of
predetermined humidity, comprising a chamber for containing
such atmosphere^, means for supplying dry air and moist air
to said chamber and means for drawing air from said
chamber, control means for controlling the relative amounts
of dry air and moist air supplied to the chamber to afford
an adjustment of humidity, means for sensing the actual
humidity of the atmosphere in said chamber and for
providing a feed-back signal to said control means.

2. Apparatus for providing an atmosphere of
predetermined humidity, comprising a chamber for containing
such atmosphere, controllable moisture removal means for
removing moisture from the atmosphere in said chamber,
means for sensing the actual humidity of the atmosphere in
said chamber and for providing a corresponding feed-back
signal to control means arranged to control said moisture
removal means so as to remove moisture from said atmosphere
only so long as the humidity in said chamber is above said
predetermined humidity.

3. Apparatus for providing an atmosphere of
predetermined humidity, comprising a chamber for containing
such atmosphere, means for supplying dry air and moist air
to said chamber and means for drawing air from said
chamber, control means for controlling the relative amounts
of dry air and moist air supplied to the chamber to afford
a coarse adjustment of humidity, and fine control means
including moisture removal means for removing moisture from
the atmosphere in said chamber, the apparatus including a
control facility controlling said dry and moist air
supplying means, and said means for drawing air from the

wo 92/21080

PCr/GB92/00910

6

chamber^ and/or controlling said moisture removal means,
said humidity sensing means providing its output signal to
said control facility.

4. Apparatus according to claim 2 or claim 3 wherein
said moisture removal means includes a cooled surface upon
which condensation of moisture from said atmosphere can
take place, to remove such moisture from said atmosphere,
and means for controlling the temperature of said surface
to control moisture removal by said moisture removal means.

5. Apparatus according to claim 3 wherein said control
facility comprises a computer.

6. A method of providing an atmosphere of pre-
determined humidity comprising mixing dry and moist air
into a chamber to afford an atmosphere, in the chamber,
which has a humidity which is slightly higher than said
predetermined humidity, and removing moisture from the
atmosphere in said chamber until said predetermined
humidity is reached.

wo 92/21080

PCr/GB92/00910

1/i

Fig. 1.

24^ 26

28

23.7

SUBSTITUTE SHEET

INTERNATIONAL SEARCH REPORT

IntcniatioDaJ ApplicarioD U

PCT/GB 92/00910

V

I. CLASSIFICATION OF SUBJECT MATTER (if s«vcrai dassiftcitioo symbols apply, indicate all)^

According to InternatioiULi Pateat Oassificatioa (IPC) or to both National Qassification and IPC

Int. CI. 5 G05D22/02

n. FIELDS SEARCHED

Minimum Documentadoo Searched

Classiflcatioa Syste

QasificatioD Symbols

Int.Cl. 5

G050 :

GOIN

Deaimeataxion Searched other than Minimum Oociuncoutioii
to the Extent that such Documents are Included In the Fields Searched*

m. DOCUMENTS CONSIDERED TO BE RELEVANT*

Categoty"

CitatioD of Document,^! with indication, whse appropriate, of the ttlevant passages >2

Rdevaat to Claim NoP

AU,A,501 831 (UNIVERSITY OF, SYDNEY) 6 April 1978
see page 2, line 1 - page 14, 'line 17; figure 1

AU,A,598 532 (NEIL KIRBY) 22 October 1987
see page 2, line 5 - page 6, line 20

AU,A,574 009 (NIPPON YUSEN KAISHA) 23 June 1988
see page lA, line 10 - page 6, line 18

US, A, 4 356 834 (LEMAY) 2 November 1982
see column 1, line 5 - column 2, line 21;
figures 1,2

FR,A,2 606 900 (JACQUIN) 20 May 1988
see abstract; claims 1-5; figure 1

1-6
1-6
1-6
1-6

1-6

Sp«dal categories of oted docuxacots :

'A' document defloing the geaerml state of the art which is not

coasidcfed to be of partiailar reievince
'E* eariier docuracot but published on or after the international

filing date

'L' document which may throw doubts on priority daira(5) or
which is cited to establish the publication date of another
citation or other special reason (as specified)

'O' document referring to an oral disclosure, usei exhibition or
other means

^P* document published prior to the international filing date but
later thaa the priority date claimed

T* later document published after the intcraadoBal filiog date
or priority date and not In conflict with the appUcatioo but
dttd to understand the principle or theory unaeriying the
invention

rSC document of particular relevance; the claimed Invcntiott
cannot be considered novel or cannot be considered to
involve an inventive step

"Y' document of particular relcvmnce; the claimed invention
cannot be considered to involve an inventive step when the
document is combined with one or more other such doot-
ments, such corabinatioa being obvious to a person slulled
In the art.

'ft' doaimeot member of the same patent family

IV. CERTIFICATION

Date of the Actual Coopletioa of the iDtemational Search

10 AUGUST 1992

Data of Mailing of this International Search Report

21. 09.92

International Searching Authority

EUROPEAN PATENT OFHCE

Signature of Authorized Officer

SCHOBERT D.A^V-

FmPCT/ISAyuOOi

dHJi

ANNEX TO THE INTERNATIONAL SEARCH ^J^ORT 9200910
dN imERNATIONAL PATENT APPLICATION NO. 9200910g^

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S:SSSL'5Sc'SSSt S STwTK^r'S^^S^^ « ««.y Civ- .^r p»p,» criofo™..-.. 10/08/92

Pafteot document
deed in search report

Publicadoa

Patent fsioily
uitfubci^s)

PublkadoB
date

AU-A-501831 28-06-79 None

AU-A-598532

28-06-90

AU-A-

7143087

22-10-87

AU-A-574009

23-06-88

None

US-A-435683*

02-11-82

None

FR-A-26G6900

20-05-88

None

aFora#redet«ta«boctt!itt«DDCx:s«eOffid«l JouriwloftbcEt^^ «/82

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